A break in afternoon rain gave Armstrong the opening he needed on the winding, cobbled circuit, which would have been treacherous if wet.

''I was lucky that the course was dry,'' Armstrong said.

As defending champion, Armstrong was the last of the 189 riders to start. He was cheered by fans as he raced through the streets of this tiny country's capital, beating Jalabert's impressive time.

The victory marked only the second time the U.S Postal Service team leader has won the event's prologue.

He won the prologue in 1999, the same year he punctuated his comeback from cancer by winning the race.

As titleholder, Armstrong had the right to wear the yellow jersey from the start, but wore his team colors instead.

''I wanted a suit that was broken in, so to speak,'' Armstrong said. ''And then, I don't know if it's right that I start in the yellow jersey, because it was last year -- it was a completely different race.''

''I wanted to look down and see a team jersey and say 'The yellow one is out there, and you have to earn that,''' he added.

Armstrong warmed up in the practice area with his wife Kristin and their three children by his side. It was the first time his family has been with him at the Tour start.

''It was special -- and it's perhaps why I was so motivated today,'' Armstrong said. ''It's becoming harder and harder for me to leave and go to the races, and leave behind the children.''

Noticeably absent from this Tour was Jan Ullrich, the 1997 Tour winner and runner-up the last two years. The German was sidelined by a knee injury in May and recently tested positive for amphetamines.

Armstrong's top challengers this year include Spaniard Joseba Beloki of Once, the third-place finisher the last two years. He completed the prologue in ninth place, 13 seconds behind Armstrong.

Didier Rous of the Bonjour team fell shortly after leaving the starting gate and had to use a replacement bike. The Frenchman sat in 163rd place, more than a minute off the pace.

The start in Luxembourg marked the 14th time the event started outside France. Sunday's first stage is a hilly, 119.35-mile run through the countryside and medieval towns of the tiny Grand Duchy of Luxembourg, one of Europe's smallest countries.

The three-week Tour covers 2,034.8 miles, making it one of the shortest ever. The race ends in Paris on July 28.